U.S. Pat. No. 8,268,637 B2 discloses label-free biosensors based upon distributed feedback (DFB) laser. In one configuration, the DFB laser comprises a replica-molded, one- or two-dimensional dielectric grating coated with a laser dye-doped polymer as a gain medium. The laser dye or other active material in the active layer is pumped via an external optical source. The stimulated emission wavelength of the laser dye is modulated, i.e. shifted, by the adsorption of biomolecules on the DFB laser biosensor's surface. The reference does not teach a spatially resolved measurement of the sample.
Hence, an improved surface refractive index detecting system would be advantageous, and in particular a system providing a spatially resolved measurement of the refractive index would be advantageous.